A064287 Number of cyclotomic cosets C of 2 mod 2n+1 such that -C is not equal to C, divided by 2.

0, 0, 1, 0, 0, 0, 1, 0, 0, 2, 1, 0, 0, 0, 3, 0, 2, 0, 1, 0, 0, 2, 1, 2, 2, 0, 1, 0, 0, 0, 5, 0, 0, 2, 1, 4, 2, 2, 1, 0, 0, 4, 1, 4, 4, 6, 1, 0, 0, 0, 1, 6, 0, 0, 1, 0, 2, 4, 3, 0, 2, 0, 9, 0, 0, 4, 3, 0, 0, 2, 1, 0, 4, 0, 5, 4, 6, 0, 1, 4, 0, 4, 1, 0, 0, 0, 3, 0, 0, 0, 1, 0, 2, 8, 1, 0, 6, 0, 1, 0, 2, 0, 3, 0, 0

Offset: 1

Author

N. J. A. Sloane, Sep 25 2001

Keywords

• nonn
• nice
• easy

Examples

			Mod 15 there are 4 cosets: {1, 2, 4, 8}, {3, 6, 12, 9}, {5, 10}, {7, 14, 13, 11}. Only the cosets {1, 2, 4, 8} and {7, 14, 13, 11} have the desired property, so a(7) = 2/2 = 1.
		

References

• F. J. MacWilliams and N. J. A. Sloane, The Theory of Error-Correcting Codes, Elsevier/North Holland, 1977, pp. 104-105.

Links

• Ray Chandler, Table of n, a(n) for n = 1..10000

Crossrefs

A006694(n) = A064286(n) + 2*a(n).

Extensions

Extended by Ray Chandler, Apr 25 2008